This invention relates to a novel thermoformable laminate comprised of a polyaryletherketone sheet and a polyvinyl fluoride sheet or film and to thermoformed articles produced therefrom.
Shaped articles can be prepared from thermoplastic sheets using a thermoforming process. Thermoforming is defined in Tool and Manufacturing Engineers Handbook (Vol. 2, 4th Edition, Society of Manufacturing Engineers, Dearborn, Mich., 1984, Charles Wick, Editor) as a process in which a thermoplastic sheet is heated to its processing temperature and, using mechanical methods or differential pressure created by vacuum and/or pressure, is forced to contact a mold surface and cooled while held to the contours of the mold until it retains the shape of the mold.
It is well known by those skilled in the art of thermoforming that processing temperatures at or above the crystalline melting points are required to form articles from semicrystalline polymers. Thus, as described in the art, the temperatures required for thermoforming polyaryletherketone sheets are in the range of 300 to 400.degree. C., where these materials melt. Polyvinyl fluoride, however, decomposes at temperatures above about 200.degree. C., so that laminates of polyarylketones with polyvinyl fluoride normally cannot be thermoformed because of polyvinyl fluoride film degradation.
It, therefore, would be desirable to provide laminates of a polyaryletherketone sheet with a polyvinyl fluoride sheet or film, such laminates being thermoformable at temperatures below 200.degree. C., without risk of thermal degradation of the polyvinyl fluoride component.